Is it important to control the efficacy of antiplatelet therapy in patients with drug-eluting stents presenting for surgery ?

Coupez C., Watremez C., Momeni M.
Cliniques Universitaires Saint Luc; Université Catholique de Louvain, Dept of Anaesthesiology, Brussels, Belgium

Background
The European guidelines recommend ticagrelor and prasugrel as the treatment of choice for Acute Coronary Syndrome (ACS) because of their superior platelet inhibition action when compared with clopidogrel.1 They are therefore often used when Drug-Eluting Stents (DES) are inserted. A meta-analysis comparing ticagrelor and prasugrel suggested that ticagrelor allows a higher platelet reactivity inhibition as compared with prasugrel.2 Resistance to the newer antiplatelet drugs, although theoretically possible, has not yet been reported.

Case Report
A DES was inserted in a 59-year-old diabetic patient after an ACS. The patient was put on dual antiplatelet therapy aspirin 80mg/day and ticagrelor 90mg 2x/day. She presented intrastent thrombosis 6 months post
DES insertion despite perfect medication compliance and was successfully treated with 2 other DES. A Multiplate electrode aggregometry realized by Multiplate® Analyzer showed no ADP-induced platelet aggregation. Ticagrelor was stopped and prasugrel 160mg was started. The patient presented 4 months later for an elective peripheral vascular surgery. A Multiplate® test was realized to confirm efficient dual antiplatelet therapy (aspirin-prasugrel). Table 1 illustrates the results of the Multiplate® test under ticagrelor (at the moment of stent thrombosis) and subsequently prasugrel therapy.

Table 1: Results of Multiplate® 
Normal range : ADP Test 607 - 963 / ASPI Test 505 - 1086 / TRAP Test
868 - 1473
Ticagrelor and Aspirin therapy : ADP Test : 684 / ASPI Test : 365 / TRAP Test : 1066
Prasugrel and Aspirin therapy : ADP Test : 397 / ASPI Test : 205 / TRAP Test : 1067

Discussion
The etiology of increased platelet activation in diabetic patients is multifactorial.3 Resistance to aspirin and/or clopidogrel is well known and especially described in diabetic patients resulting in an increased cardiological use of newer antiplatelet drugs. We describe a first case of biological and clinical resistance to ticagrelor. Patients on dual antiplatelet therapy for DES and presenting for elective or emergency surgery should systematically be tested for efficacy of their antiplatelet treatment in order to adapt the perioperative management.

References
1. EurHeartJ2012;33:2569-619;
2. JThromHaemost2015;13:931-42; 3. CurrCardiovascRiskRep2015;9:4

Learning Points
1. This case illustrates that resistance to newer antiplatelet medications can occur.
2. Point-of-Care functional platelet tests are easy to perform and can rapidly confirm the efficacy of antiplatelet therapy in patients with DES.

Is it important to control the efficacy of antiplatelet therapy in patients with drug-eluting stents presenting for surgery?